1. Field of the Invention
Devices for transmitting power have existed in various forms since Leonardo DeVinci. The mechanical art has evolved from pegs in the circumference of a wheel to the present day sophisticated gearing sets.
As the environment in which a particular transmission must function changes, so too must the transmission provoke creative solutions. In the present instance, significant power is required to be transmitted through a restricted space, e.g., a drill or well casing, in which the interior diameter could be as little as 4 inches, and the working end of the drill string may be thousands of feet down from the power source.
It has been shown that transmission of power by gear sets in restricted spaces can be significantly increased by utilizing a configuration whereby multiple helical gears are arranged on a common spline shaft, as given in Morrow U.S. Pat. No. 5,297,147. As space becomes ever more restrictive and the gears, by necessity, decrease in size, the power capable of being transmitted by a gear set quickly becomes limited by the decreasing diameter of the common spline shaft. It is this problem which the present invention seeks to solve.
2. Overview of the Prior Art
Bruce Morrow, an acknowledged expert in the field, successfully addresses the issue of transmitting significant power via a novel gear train in a restricted space in his U.S. Pat. No. 5,927,147, in which retainers were disclosed. Morrow U.S. Pat. No. 6,334,368 [load sharing with planetary gearing]; U.S. Pat. No. 6,338,691 [a planetary system with helical gearing]; and U.S. Pat. No. 6,374,689 are examples of Morrow's work.
Hawkins U.S. Pat. No. 6,264,138 relates to a gear set for use in a turbo prop system for gas turbine engines, while Gotoh U.S. Pat. No. 6,666,103 discusses support for an intermediate shaft in a transmission, as does Jessup U.S. Pat. No. 4,641,543, where opposite and unequal helical angles are employed to balance loading.
The foregoing are merely indicative of the state of the art and in no way diminishes the novelty or value of the present invention.